Granted, though, finding someone really tall and muscular who's also a good actor is tricky. So that might justify going CGI, although it seems extravagantly expensive in a case like this, given that it's easy to make actors look bigger with costuming, camera angles, and the like.

I mean, really, if the X-Men movies got hung up on height, Hugh Jackman would never have qualified to be Wolverine.

Ah, but they never tried to make Jackman look short. And while you're correct about making actors look bigger, there are limits, especially when it comes to brawling. It's a lucky thing for PJ and Co. that Tolkien never wrote a Frodo/Gandalf fistfight.